Magnesium is conventionally produced by electrolysis of magnesium chloride by the reation EQU MgCl.sub.2 .fwdarw.Mg+Cl.sub.2.
In the Dow process, for example, the electrolysis cell is constructed of steel with the cathodes welded to the tublike container that holds the bath. The cell is fitted with a refractory cover through which multiple cylindrical graphite anodes pass. The anodes are suspended such that they can be adjusted independently to maintain the proper spacing and centering with respect to the respective cathodes as the anodes are consumed.
The cell operates at temperatures of about 700.degree.-720.degree. C. at a pressure slightly below atmospheric pressure in order to facilitate collection of chlorine gas, which is a by-product of the electrolysis. The graphite anodes used in the cell, which are consumed by oxidation due to the presence of impurity water in the bath, are fed into the cell through relatively air tight seals at the top of the cell. Because of the low pressure in the cell, air is drawn through the porosity of the graphite anodes and oxidizes the graphite in the region thereof below the top of the cell and above the surface of the molten electrolyte. Graphite is consumed at approximately 100 g/kg magnesium product.